As prior art for increasing the thickness of an end part of a tube, for example, there is the one disclosed in PLT 1. In the method of PLT 1, as shown in FIG. 1A, a tube 1 is placed in the middle of an upper die 2 and a lower die 3, then an upsetting punch 4 is pushed against this in the arrow direction to increase the thickness of an end part of the tube 1 as shown in FIG. 1B.